Keep your cool: Overwintering physiology in response to urbanization in the acorn ant, Temnothorax curvispinosus

Is there evolutionary divergence in Acorn Ant Overwintering physiology across the urbanization gradient? We expected that warm adapted urban populations would have lower performance in cold tolerance (longer recovery time) and higher metabolic rate at cold temperatures while expressing higher heat tolerance (higher temperature to loss of muscle control). We also expected greater population loss in urban populations under cold acclimation temperatures. To test our hypotheses, we ran a common garden rearing design for field caught urban and rural ants under overwintering conditions and then tested their heat tolerance, cold tolerance, metabolic rate and survival. We found no differences in cold tolerance or metabolic rate in urban and rural populations but did find higher heat tolerance in urban populations. The following descriptions show what each data set and R script sets up: Scripts R code for each physiological measure under overwintering conditions - OvW_Count: worker count / Survival: collected data on the number of workers at the start and end of the experiment - OvW_MR_script: Metabolic Rate: collected routine metabolic rate (mLCO2 / min) at two temperatures (4 and 10 C) for all populations. - OvW_CCRT: Chill Coma Recovery Time (CCRT): cold tolerance measure of recovery time from an acute cold temperature stress that induces chill coma (ours was measured at -10 C) and measured as time until leg / antennae movement. - OvW_CTmax: Critical Thermal Maximum (CTmax): heat tolerance measure of muscular control under a dynamic ramping assay measured as the temperature at which loss of muscle control was observed. Metadata for each data file description of variables within each dataset ### CCRT - CCRT csv file in minutes; code changes to seconds for modeling as an integer - Treatment (source population: urban or rural) and Collection season are factor variables - Colony ID is randomly generated value ### CTmax - CTmax csv file: ctmax in degrees C - Treatment (source population: urban or rural) and Collection season are factor variables - Colony ID is randomly generated value ### Worker Count / Survival - Worker start and end are the number of workers at the beginning (0) and end (4) months of the experiment - Source population (urban or rural) is a factor variable - Colony ID is randomly generated value ### metabolic rate - mean MR = average metabolic rate in CO2 (mL CO2/min) - mean MR RA = avg metabolic rate in CO2 rolling average (not used in analyses) - Chamber index = chamber where colony was; chamber 8 = control or blank container - Q10 = thermal sensitivity quotient of the two metabolic rates at two temperatures raised to the 10th power divided by the temperature difference - Collection date = similar to collection season factor from ccrt and ctmax files above - Source.pop = factor variable (urban or rural) - Colony ID is randomly generated value橡子蚁（Acorn Ant）越冬生理学沿城市化梯度是否存在进化分化？ 我们推测，适应温暖城市环境的种群在耐寒性上表现更劣（恢复时长更长），且低温环境下代谢率更高，同时耐热性更强（肌肉控制丧失时的临界温度更高）。我们还推测，低温驯化条件下城市种群的种群损失率更高。 为验证上述假说，我们采用同质园饲养实验设计，对野外捕获的城市与乡村蚂蚁开展越冬条件下的饲养实验，随后检测其耐热性、耐寒性、代谢率与存活率。研究结果显示，城乡种群在耐寒性与代谢率上无显著差异，但城市种群的耐热性显著更高。 以下分别说明各数据集与R脚本的设置： ### 脚本 越冬条件下各项生理指标检测对应的R代码： - OvW_Count：工蚁计数/存活率：记录实验起始与结束时的工蚁数量 - OvW_MR_script：代谢率：针对所有种群，在4℃与10℃两个温度下检测常规代谢率（mLCO₂/分钟） - OvW_CCRT：冷昏迷恢复时长（Chill Coma Recovery Time, CCRT）：耐寒性指标，衡量急性低温胁迫诱导冷昏迷后的恢复时长（本实验在-10℃下测定，以足或触角开始运动的时间作为判定标准） - OvW_CTmax：临界热最大值（Critical Thermal Maximum, CTmax）：耐热性指标，通过动态升温实验测定肌肉控制丧失时的温度。 ### 各数据文件元数据 各数据集内变量说明： #### CCRT数据集 - CCRT.csv：数据单位为分钟，建模时会转换为秒并以整数形式存储 - 处理组（源种群：城市或乡村）与采集季节为分类变量 - 蚁群ID为随机生成的数值 #### CTmax数据集 - CTmax.csv：ctmax单位为摄氏度 - 处理组（源种群：城市或乡村）与采集季节为分类变量 - 蚁群ID为随机生成的数值 #### 工蚁计数/存活率数据集 - Worker start与Worker end分别为实验开始（第0个月）与结束（第4个月）时的工蚁数量 - 源种群（城市或乡村）为分类变量 - 蚁群ID为随机生成的数值 #### 代谢率数据集 - mean MR：平均代谢率，单位为mL CO₂/分钟 - mean MR RA：代谢率滚动平均值（未纳入后续分析） - 呼吸室编号（Chamber index）：蚁体所处的呼吸室编号，其中8号室为对照或空白容器 - Q10：温度敏感性商值，即两个温度下的代谢率比值经10次幂后除以两者的温差 - 采集日期：与上述CCRT与CTmax文件中的采集季节分类变量含义一致 - Source.pop：分类变量（取值为城市或乡村） - 蚁群ID为随机生成的数值